创建一个简单的迭代器

 1 class IterateEnumertor : IEnumerator
 2     {
 3         private readonly IterateCollection collection;
 4         private int index;
 5         private object current;
 6         public IterateEnumertor(IterateCollection collection) 
 7         {
 8             this.collection = collection;
 9             index = 0;
10         }
11 
12         public object Current
13         {
14 
15             get { return current; }
16         }
17 
18         public bool MoveNext()
19         {
20             if (index + 1 > collection.Count) { return false; }
21             else 
22             {
23                 this.current = collection[index];
24                 index++;
25                 return true;
26             }
27         }
28 
29         public void Reset()
30         {
31             index = 0;    
32         }
33     }

 1   static void Main(string[] args)
 2         {
 3             string[] strarr = { "刘诗诗","陈乔恩","刘亦菲"};
 4             IterateCollection collection = new IterateCollection(strarr);
 5             foreach(string str in collection)
 6             {
 7                 Console.WriteLine(str.ToString());
 8             }
 9             Console.Read();
10         }

摘要：1 想要可以被迭代，就要实现IEnumerable,或者IEnumerable<T>,并且重写GetEnumerator()；方法，得到一个迭代器

     2 在C#1.0中迭代器要自己写，通过实现IEnumerator,或者IEnumerator<T>,并且重写MoveNext();和Reset();方法

C#2.0简化了迭代器的实现

1        public IEnumerator GetEnumerator()
2         {
3             //return new IterateEnumertor(this);
4             for (int index = 0; index < strarr.Length; index++) 
5             {
6                 yield return strarr[index];
7             }
8         }

摘要 yield return 关键字告诉编译器去执行实现过程，我们程序员就减少了编码量